Evaluation of a large-scale bridge strain, temperature and crack monitoring with distributed fibre optic sensors

Royal Institute of Technology (KTH), Stockholm, Sweden
Journal of Civil Structural Health Monitoring 06/2011; 1(1):37-46. DOI: 10.1007/s13349-011-0004-x

ABSTRACT Many structures like bridges are ageing and the necessity to measure the uncertain parameters is relevant. Crack-related parameters
can be measured with traditional techniques like crack gauges and displacement transducers. A method that can detect and localise
cracks as well as measure crack width is most favourable. Several distributed and quasi-distributed systems were introduced
to the market and tested in recent years. This paper presents a large-scale Structural Health Monitoring project based on
stimulated Brillouin scattering in optical fibres for an old bridge. The Götaälv Bridge is a continuous steel girder bridge
with concrete bridge deck. Steel girders suffer from fatigue and mediocre steel quality and some severe cracking and also
a minor structural element collapse have taken place. The system installed on the bridge measures strain profiles along the
whole length of the bridge and detects cracks that are wider than 0.5mm. Procedures like factory acceptance test, site acceptance
test, laboratory testing and field testing are presented and analysed. Innovative technology was developed, tested and applied
on the bridge. Heuristic knowledge was collected; conclusions are presented and discussed for future development.

KeywordsBridges–Field testing and monitoring–Maintenance and inspection

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    • "There is a great variety of optic sensors, which are used both for industrial applications and for the structural control of civil structures [7] [8] [9] [10] [11] [12] [13]. The several research recently published show the interest from the scientific community to the issue of structural health monitoring by means of last generation sensors [14] [15] [16]. "
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    ABSTRACT: The paper presents a study about the monitoring of a pre-stressed reinforced concrete viaduct in Bari (Italy), by means of an optical fiber system embedded into the structural elements. The application case had two objectives: controlling the structural efficiency during the phases of construction, and allowing, in the future, the periodical check of the structural performance under service loads. Sensors were directly anchored to the prestressing strands during the manufacturing phases of the precast beams. By processing and analyzing the data acquired by the system during the different construction phases, it was possible to assess the strain variations related to load increments and stress losses, by comparing them with expected theoretical values. The specific case study shows that the availability of real-time monitoring procedures is nowadays a precious tool for checking the structural safety of critical facilities, in particular bridges.
    10/2014; 2. DOI:10.1016/j.csndt.2014.06.002
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    • "Structural monitoring has become nowadays an important research area involved in the structural integrity assessment of civil infrastructures. Engineering communities have shown an increasing interest to monitor bridges (Enckell et al., 2011; Ye et al., 2013), tunnels (Lindenbergh et al., 2005; Puente et al., 2014; Sharma et al., 2001) and other structures (Valença et al., 2013) and to detect damage at the earliest stages. Specifically, rubble mound breakwaters (Corredor et al., 2013) are commonly employed to protect important coastal areas such as ports, marinas or beaches from the effects of attacking ocean waves. "
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    ABSTRACT: Rubble mound breakwaters are coastal defense structures that protect harbors and beaches from the impacts of both littoral drift and storm waves. They occasionally break, leading to catastrophic damage to surrounding human populations and resulting in huge economic and environmental losses. Ensuring their stability is considered to be of vital importance and the major reason for setting up breakwater monitoring systems. Terrestrial laser scanning has been recognized as a monitoring technique of existing infrastructures. Its capability for measuring large amounts of accurate points in a short period of time is also well proven. In this paper we first introduce a method for the automatic extraction of face geometry of concrete cubic blocks, as typically used in breakwaters. Point clouds are segmented based on their orientation and location. Then we compare corresponding cuboids of three co-registered point clouds to estimate their transformation parameters over time. The first method is demonstrated on scan data from the Baiona breakwater (Spain) while the change detection is demonstrated on repeated scan data of concrete bricks, where the changing scenario was simulated. The application of the presented methodology has verified its effectiveness for outlining the 3D breakwater units and analyzing their changes at the millimeter level. Breakwater management activities could benefit from this initial version of the method in order to improve their productivity.
    06/2014; II-5:385-391. DOI:10.5194/isprsannals-II-5-289-2014
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    • "In other words, a sensor in direct contact with an anomaly would successfully detect and localize the damage; however, the reliable identification of any anomalies that are not in direct contact with a sensor is challenging (Glisic and Verma 2011). Distributed FOS greatly improve spatial resolution in crack detection (e.g., Enckell et al 2011, Glisic and Inaudi 2012, Feng et al 2013), but they are inefficient for coverage of large surface areas. In general, there are two main sensing methods applied for damage detection: indirect sensing and direct sensing. "
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    ABSTRACT: Increasing concerns regarding the conditions of civil structures and infrastructure give rise to the need for efficient strategies to identify and repair structural anomalies. 'Sensing sheets' based on large-area electronics consist of a dense array of unit strain sensors. These are an effective and affordable structural health monitoring tool that can identify and continuously monitor the growth of cracks in structures. This paper presents a study on the quantitative relationship between crack width and strain, the latter measured by an individual sensor that would be part of a sensing sheet. We investigate the sensitivity of thin-film full-bridge strain sensors to concrete cracks by conducting laboratory experiments in temperature-controlled settings. The results show a distribution of near-linear relationships with an average sensitivity of 31 µε µm−1. Experiments were also conducted to investigate the effect of crack position and orientation with respect to the sensor, and it appears that both variables affect the sensitivity of strain sensors to cracks. Overall, this study confirms that full-bridge resistive strain sensors can successfully detect and quantify cracks in structural materials and are therefore appropriate as part of a dense array of sensors on a sensing sheet.
    Measurement Science and Technology 05/2014; 25(7):075602. DOI:10.1088/0957-0233/25/7/075602 · 1.35 Impact Factor
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